1. Field of the Invention
This invention relates to diode lasers and more particularly to diode laser illumination devices having a flat uniform intensity distribution in lieu of Gaussian intensity distribution. The laser devices consist of a solid state laser diode in combination with optical elements for collimating, shaping and focusing the beam. These optical elements include the compound lenses, graded index lenses, prisms or other elements in accordance with the specific application of the laser.
2. Description of the Prior Art
Diode lasers emit a diverging beam of light having a Gaussian distribution. For spatial light modulation applications, there is a need for uniform distribution rather than Gaussian. To fulfill the requirements, an aspheric or a holographic pair of lenses is needed; but, they are very expensive or subject to effects of humidity and pressure. See "Applied Optics" published data:
Vol. 22 p 3644, 1983 Chang-Yuan et al: "Reshaping Collimated Laser Beam with Gaussian Profile to Uniform Profile Using Holography". PA1 Vol 19 p. 3545, 1980 P. W. Rhode et al: "Refractive Optical System for Irradiance Redistribution of Collimated Radiation Using Aspherical Elements" PA1 "Optics and Laser Technology" Vol. 14, Pg 159; 1982, D. Shafer; and PA1 U.S. Pat. No. 3,476,436 describes a spherical lens pair and mentioned four spherical elements as a possibility for changing the intensity distribution. Also, in the prior art, the diode laser beam, being divergent about 20 degrees perpendicular to the junction and 10 degrees parallel to the junction, is reshaped to a circular beam using 2 prisms by a method described in U.S. Pat. 4,609,258 to Adachi et. al.
A beam from a Gas laser, He--Ne or CO.sub.2 was discussed in